Labour's election strategists are pressuring Gordon Brown to make firm pledges on future tax rates.

The Times says that the party's high command has doubts about continuing with the tactic of pledging not to raise either the basic or higher rate of income tax, but not ruling out increasing Treasury revenues in other ways.

The prime minister told MPs yesterday that Labour had kept all its promises on taxation, adding: "In respect of any pledges we make at the next election you will have to wait for our manifesto [and], of course, there will be a Budget in the meantime."

However, one "senior source" told the Times: "It is quite difficult to build an election campaign, based on the foundation stone of our economic success, if Gordon is refusing to tell us what he plans to do about taxation.

"We cannot necessarily wait for the Budget, which will probably be just before the election begins."